JP-10-201001A describes a vehicle presence notification apparatus which notifies a presence of a vehicle for a circumference of the vehicle by outputting a notification sound. The vehicle presence notification apparatus generates the notification sound using a dynamic speaker which directly generates audible sound (acoustic wave with audible frequency).
The notification sound such as false engine sound, chord, voice sound, or music is required not to be felt noisy while an alarm (warning) sound produced by an alarm device such as horn may be noisy to some extent. For example, low-pitched sound with frequency component of 600 Hz or less is mixed in the notification sound to reduce the noisiness.
The dynamic speaker is what is called a cone speaker in which a cone paper (diaphragm) directly drives air. In such dynamic speaker, it is difficult to produce the low-pitched sound, so it is required to make the cone paper larger to raise the sound pressure of the low-pitched sound like a woofer. However, it is difficult to mount the large-sized speaker to the vehicle, and the large-sized speaker causes increase in the cost.